Heterogeneous monopropellant compositions and thrust producing method

ABSTRACT

1. Novel thixotropic, monopropellant compositions comprising a mixture of a fuel selected from the group consisting of inorganic carbides, inorganic borides and inorganic boride-carbide mixtures, a liquid oxidixer selected from the group consisting of nitric acid, nitric acid enriched with NO2, nitric acid enriched with NO2 and HF, nitrogen tetroxide, hydrogen peroxide, and perchloric acid dihydrate and a thixotroping agent selected from the group consisting of carbon, silica, clay, and mixtures thereof. 23. A method of developing thrust in a reaction motor, having a combustion chamber and a discharge opening, comprising the steps of igniting in said combustion chamber, a hterogeneous propellant composition of from about 15-40 parts by weight of a solid fuel selected from the group consisting of inorganic carbides, inorganic borides and inorganic boride-carbide mixtures, from about 60-95 parts by weight of a liquid oxidizer selected from the group consisting of perchloric acid dihydrate, concentrated H2O2 and N2O4, and up to about 10 parts by weight of optional propellant adjuvants and a thixotroping agent selected from the group consisting of carbon, silica, clay, and mixtures thereof; and venting the combustion gases derived therefrom through said discharge opening.

United States Patent 1 Tannenbaum Nov. 25, 1975 HETEROGENEOUS MONOPROPELLANT COMPOSITIONS AND THRUST PRODUCING METHOD [75] Inventor: Stanley Tannenbaum,Morristown,

[52] U.S. Cl. 60/217; 149/22; 149/74; 149/88; 149/89; l49/l08.2; l49/108.8; 149/109.2 [51] Int. Cl. C06D 5/10 [58] Field of Search 149/1, 17-19, 149/22, 74, 88,89, 108.2, 108.8, 109.2; 60/35.4, 217

[56] References Cited UNITED STATES PATENTS 3,009,800 11/1961 Swimmer 149/22 X 3,069,300 12/1962 Damon et al. 149/22 3,092,959 6/1963 Scurlock et al... 60/217 3,097,479 7/1963 Reipold 60/217 3,691,769 9/1972 Keilbach et a1 60/217 Primary Examiner-E. A. Miller Assistant Examiner-Benjamin R. Pagett Attorney, Agent, or FirmStanley A. Marcus; William R. Wright, Jr.

EXEMPLARY CLAIM 1. Novel thixotropic, monopropellant compositions comprising a mixture of a fuel selected from the group consisting of inorganic carbides, inorganic borides and inorganic boride-carbide mixtures, a liquid oxidixer selected from the group consisting of nitric acid, nitric acid enriched with N0 nitric acid enriched with NO and HF, nitrogen tetroxide, hydrogen peroxide, and perchloric acid dihydrate and a thixotroping agent selected from the group consisting of carbon, silica, clay, and mixtures thereof.

23. A method of developing thrust in a reaction motor, having a combustion chamber and a discharge opening, comprising the steps of igniting in said combustion chamber, a hterogeneous propellant composition of from about 1540 parts by weight of a solid fuel selected from the group consisting of inorganic carbides, inorganic borides and inorganic boride-carbide mixtures, from about 60-95 parts by weight of a liquid oxidizer selected from the group consisting of perchloric acid dihydrate, concentrated H 0 and N 0 and up to about 10 parts by weight of optional propellant adjuvants and a thixotroping agent selected from the group consisting of carbon, silica, clay, and mixtures thereof; and venting the combustion gases derived therefrom through said discharge opening.

36 Claims, N0 Drawings HETEROGENEOUS MONOPROPELLANT COMPOSITIONS AND TI-IRUST PRODUCING METHOD This invention relates to novel heterogeneous monopropellant compositions.

More particularly, this invention concerns the preparation of highly energetic, thixotropic propellant compositions which are superior in certain respects to presently utilized solid or liquid propellant compositions.

The novel, thixotropic propellant compositions of this invention are composed essentially of:

A. Carbide and/or Boride fuels B. Liquid Oxidizer C. Thixotroping or Gelling Agents and optional propellant adjuvants The use of liquid propellant compositions offers several significant advantages over comparable solid propellant compositions. For example, liquid propellant formulations are much more energetic than currently used solid compositions and have greater specific impulse. Increased specific impulse gives the missile a longer range and a higher velocity for the same weight of propellant charge.

A further superiority of liquid propellants over solid propellants is that the combustion of liquid propellants can be mechanically controlled during flight. Combustion can be stopped and started at will, by controlling the flow of the propellant into the combustion chamber. Reducing the flow of the propellant into the combustion chamber decreases the thrust of the propellant, while increasing the flow rate has the opposite effect. Since the heterogeneous propellants of this invention are in the liquid state when utilized, their flow rate can be controlled mechanically. This control is accomplished by adjusting the pumps and valves in the missiles fuel transport system.

The significance of mechanical control is that all liquid propellant systems have a built-in throttleability feature that is absent in solid propellants. Throttleability allows the missiles velocity to be varied, controls the attitude of the missile, makes evasive action possible, permits the rendezvous of two or more space ships during flight and reduces the hazards of landing.

In contrast, since solid propellants cannot flow, no comparable fuel transport takes place and no comparable control of combustion through varying the flow rate is possible. In fact, after ignition, using the present technology, no method is presently available to control the combustion of the solid propellant charge after. ignition. Thus, the difference of physical state alone makes all solid propellants inherently disadvantageous to liquid propellants for many applications.

Further significant disadvantages of solid propellants compared to liquid propellants arise in a number of ways because of the extreme sensitivity of solid propellants toward temperature and pressure fluctuations. This occurs both during storage and use. For example, the temperature of a solid propellant grain substantially influences performance. A given grain of solid propellant will produce more thrust on a hot day than on a cold day. Further, the physical state of the solid propellant is effected by temperature extremes. For instance, at very low temperatures many solid propellants become brittle and subject to cracking. Cracks in the propellant grain increase the propellants burning rate significantly and can cause a fracture or explosion. On the other hand a solid propellant exposed to high temperatures prior to firing can lose its shape and have its performance advesely affected. This sensitivity of solid propellants toward temperature fluctuation necessitates expensive storage under constant temperature prior to use.

For all of the foregoing reasons solid propellants are presently inferior to comparable liquid propellant compositions for many applications.

Even more advantageous than liquid propellants per se are liquid monopropellant compositions. These monopropellant formulations unlike bipropellant formulations contain oxidizer, fuel and any other required adjuvant materials, combined and stored as a sisngle formulation. Since these formulations already have sufficient oxygen no additional source of oxidizer is required and they can be handled after formulation as a single complete composition. Thus, only one storage tank and but one pumping system is needed both on the grouond and in the missile. In contrast, bipropellant formulations consist of at least two separate compositions since the fuel and oxidizer components are kept physically separate until they are injected into the missiles combustion chamber. Both at the storage facility and in the missile, duplicate storage and pumping systems are essential. Furthermore, in many instances where the oxidizer is a gas such as oxygen, the oxidizer must be refrigerated under high pressure. Halving the pumping and storage requirements, particularly the pumpimg system, reduces the mechanical complexity of the fuel transport system and decreases the likelihood of mechanical malfunction of the missile. In addition, the need for only one set of storage and pumping facilities greatly simplifies design and construction of the missile, decreases the weight of the hardware and increases the fuel load of the missile. An ancillary but not unimportant result of simplifying the transport and storage systems is the reduction of maintenance time and maintenance and storage costs.

Unfortunately, while monopropellant formulations offer all of the above enumerated adantages over bipropellant formulations, these advantages heretofore have been largely unrealized. The reasons for this have been several. Among other things, monopropellant compositions have been too easily ignited, become unstable upon prolonged storage, too readily detonate upon being disturbed and give erratic and relatively poor performance.

For example, the prior art monopropellant compositions are typified by the following: heptane-nitrogen tetraoxide, n-propyl nitrate, nitromethane, propargyl nitrate-nitramine and the like. All of these materials suffer from the failing of poor thermal stability, high sensitivity toward detonation and/or the tendency to deteriorate under prolonged storage. Poor thermal stability requires refrigerated storage, while a high sensitivity toward detonation by shock makes the propellants hazardous to store, transport and use. The deterioration ofpropellants after prolonged storage causes erratic performance and makes it continually necessary to substitute fresh propellant for aged propellant in order to maintain the initial high specific impulse. These stability factors among others greatly negate the value of the liquid monopropellants particularly in military retalitary weapons.

An additional disadvantage of bipropellant liquids oxidizer to fuel ratio and the narrow margin of ma]- function allowed in the performance of the fuel metering and injection system.

While the oxidier to fuel ratio is extremely critical to performance in all liquid propellants, in monopropellants the demands are much less stringent. This is because the oxidizer is added to the fuel during formulation and prior to use. Therefore the critical oxidizer to fuel ratio in monopropellants can be accurately determined and corrected if necessary to assure optimum performance prior to firing. In bipropellants this adjustment of oxidizer to fuel ratio cannot be made prior to firing. The reason for this is that the oxidier and fuel are separately stored until they are injected into the missile combustion chamber for use. Thus the ratio of oxidizer to fuel in the final propellant mixture is determined only at the instant of firing and cannot be corrected. Since the metering device like any complex mechanism is subject to failure, a deviation or even abortion of the missile flight can result.

Since this malfunction cannot be foreseen until it occurs no preventive measurers are possible. In a similar vein, because of the losses of fuel and oxidizer which are known to occur because of the injection and combining of the separate streams of fuel and oxidizer in the missile combustion chamber, it is necessary to store an additional supply of both propellant components in the rocket.

These losses of fuel and oxidizer are an inherent part of bipropellant systems and are referred to as outage losses. The extra weight of the outage reservoir reduces the payload the missile could carry and hence is disadvantageous. All of these shortcomings of bipropellant liquids are absent in monopropellants since the propellant is premixed and requires no metering.

For the above reasons among many others, the preparation of liquid monopropellant formulations which retain their initial high specific impulse and/or density impulse after prolonged storage is to be desired. Especially valuable would be liquid propellant formulations which retained their high specific impulse and/or density impulse yet do not become hypersensitive to detonation by shock. This combination of a highly energetic liquid propellant charge relatively insensitive to accidental detonation would be a major advance in the propellant art. Ideally these formulations would combine a low freezing point with the aforementioned properties and could be prepared from commercially available innocous components and would have thixotropic properties. The low freezing point would prevent freeze-up during flight or storage while the thixotropic state would allow the formulations to be stored as a solid and pumped as a liquid.

Thus it is an object of this invention among others to prepare highly energetic, monopropellant formulations.

It is an additional object of this invention to prepare monopropellant compositions which retain their original high specific impulse and/or density impulse after long periods of storage at ambient or even higher temperatures.

It is yet another object of this invention to prepare liquid monopropellant compositions which are not readily subject to accidental ignition.

Yet another object of this invention is to prepare liquid monopropellant compositions which are insensitive to detonation by vibrational or thermal shock.

A further object of this invention is to prepare liquid propellant compositions having a low freezing point and thixotropic properties.

It is still another object of this invention to prepare highly energetic liquid propellant compositions from readily available and individually safe components.

Other objects of this invention will become apparent to those skilled in the propellant art by a further reading of this patent application.

These objects among others are achieved by the heterogeneous monopropellant compositions and processes described herein.

In practice, novel and superior thixotropic propellant compositions are derived by preparing uniform mixtures of (a) a finely divided solid inorganic fuel selected from the group of inorganic carbides, borides and carbide-boride mixtures (b) liquid oxidizer and (c) thixotroping agents with or without propellant adjuvants.

The propellant compositions of this invention consist essentially of:

A. from about 15 to 40 parts by weight of a finely divided solid fuel selected from the group consisting of inorganic borides, carbides and boride-carbide mixtures.

B. from about 60 to parts by weight of liquid oxidizer.

C. up to about 10 parts by weight of thixotroping agents with or without optional propellant adjuvants. These latter propellant adjuvants include surface active agents, conditioning agents, modifiers and the like which while not necessary for operable propellant compositions, are desirable for optimum performance. The propellant adjuvants change, modify or impart to the propellant certain desirable physical and combustion characteristics so that they can be most effectivly used. Typical adjuvants include surface active agents, viscosity modifiers, combustion catalysts, stabilizing agents and the like. Where such adjuvants are used they will more customarily comprise between about /2 to 6 parts by weight of the final propellant compositions.

The above components of the propellant composition are thoroughly mixed or blended to form a uniform thixotropic mixture then pumped into the rocket motor as a viscous liquid which soon sets to a gel. When the propellant is to be ignited it is exposed to a shearing force converting it to a pumpable liquid. The liquid is then pumped into the combustion chamber for use. The pumping procedures are well known in the propellant art. Since the propellant compositions contain at least three classes of ingredients, it is essential for satisfactory performance that the composition be uniform in content. Thus throughout this disclosure and claims the propellant compositions referred to are understood to be those uniform in content.

A. Fuel The fuels referred to throughout this application are selected from the group of inorganic carbides and borides and mixtures of these inorganic carbides and borides. These inorganic carbides and borides can be further broken down into metallic and non-metallic carbides and borides. Illustrative non-metallic carbides inelude among others, boron, silicon, zirconium, tungsten, and the like. Typical metallic carbides among others include beryllium, calcium, aluminum, and the like. Illustrative non-metallic borides include silicon, zirconium and tungsten. Suitable metallic borides include aluminum, beryllium calcium, etc. While all of the above carbides and borides are better than average fuels in the inventive propellant compositions, as in any large group, certain members of the group are advantageous to the group as a whole and are preferred. Thus by far the most preferred fuels in the inventive propellant compositions are boron carbide, silicon carbide and silicon boride as well as mixture of these fuels. Less preferred fuels are the calcium, aluminum and beryllium carbides and borides. Fuels of more marginal interest are the other borides and carbides enumerated above.

B. Liquid Oxidizers The liquid oxidizers of this invention are of diverse structure and origin. Among the various oxidizers which can be used are the following: nitric acid, nitric acid enriched with NO (RFNA), and nitric acid enriched with NO: and HF (IRFNA and HIRFNA) nitrogen tetroxide (N 0,), concentrated hydrogen peroxide (H 0 perchloric acid (concentrated) and the like. The preferred oxidizers of this invention are HIRFNA whose composition is disclosed infra, concentrated H 0 N 0 and perchloric acid dihydrate. These oxidizers are preferred because of their low cost; commercial availability and most important, because of the highly energetic propellant compositions that are produced when they are used in conjunction with the aforenamed fuel components.

C. Thixotropie Agents or Gelling Agents These agents which are alternatively referred to as thickening agents are used to thicken the propellant compositions so that they can be stored as thixotropic solids, yet under a shearing force will revert to the liquid state. These gelling or thickening agents can be present in amounts ranging from 0 to 6 parts by weight or higher. More generally the thickener will be used in amounts ranging from 1 to 4 parts by weight. The exact amounts used will depend upon the type and amount of the particular fuel and oxidizer used as well as the thickner employed. An abbreviated but illustrative list of thickeners includes among others: the preferred thickener powdered carbon, the various anhydrous and particulate colloidal silicas, and colloidal clays such as bentonite.

D. Optional propellant adjuvant This is the generic designation used to describe the various conditioning, modifying agents, solvents and the like used to produce optiimum performance from the propellant compositions of this invention. These adjuvants ordinarily make up a minor proportion of the final propellant composition, seldom exceeding 10 parts by weight of the propellant composition and more typically comprising 0 6 parts by weight of the compounded propellant exclusive of thixotropic agents. The adjuvants listed previously are the most important utilized although many other adjuvants can be employed if desired.

E. Compounding the Propellant Formulations In preparing the novel liquid propellant formulations of this invention, several compounding procedures among many can be followed. The following represents the preferred formulative procedure:

The weighted, dry solid fuel ingredient(s) of the formulation are mixed until a homogeneous and uniform solid mixture is obtained. The mixing or blending operation can be accomplished using any number of commercial tumblers, blenders, agitators or mixers. Since the components are not detonable both individually and as a mixture, no special precautions in mixing need be taken. When the solid ingredients have been satisfactorily blended, they are blended into the required amount of oxidizer until a highly viscous liquid thixotropic mixture is obtained. This gelled propellant mixture is pumped into a rocket engine as a viscous liquid and rapidly sets to a heavy gel. When the gel is exposed to a shear force, it liquifies and its viscosity and flow properties will then depend on the rate of shear. At this stage its flow rate into the missile combustion chamber can be controlled mechanically as is the case in a typical liquid propellant composition.

Because of their exceptional stability, the novel heterogeneous propellants of this invention are preferably ignited using anyone of several possible techniques. One method is referred to as the hypergolic technique. In this method a small amount of chemical agent reactive with one or more of the propellant components is injected into the missiles combustion chamber with the flow of propellant mixture. The ignition is initiated by the reaction of chemical agent with the propellant components and the propellant once ignited burns smoothly. A satisfactory chemical agent for this purpose among others is unsymmetrical dimethyl hydrazine.

In a second method, the combustion is initiated using a squib of solid propellant. The ignition of the solid propellant can be electrically actuated.

F. Preferred Heterogeneous Monopropellant Compositions As indicated supra many different factors are involved in determining whether a given propellant composition is to be favored over another. Among these factors are high specific impulse, high density impulse, insensitivity toward detonation, cost, availability of the components as well as the type of use contemplated. For use as rocket propellants the most preferred heterogeneous monopropellants consist essentially of the following:

15 to 40 parts by weight of a fuel selected from the group consisting of silicon carbide, boron carbide and silicon boride.

60 to 95 parts by weight of an oxidizer selected from the group consisting of perchloric acid dihydrate, HIRFNA, nitrogen tetroxide and concentrated hydrogen peroxide (above and from about 1 to 6 parts by weight of thixotroping or gelling agent.

HIRFNAs composition is given below:

72.0 parts by weight fuming HNO 26.8 parts by weight N 0 0.7 parts by weight HF 0.8 parts by weight H O The workings of this invention can be shown more clearly by the typical embodiments which follow below:

EXAMPLE 1 A 21.4 parts by weight portion of SiB 2.5 parts by weight of carbon black (having a particle size below 1 micron) and a surface area of 6470 sq. meter/gram and a bulk density of 6.25 lbs/cu.ft.) and 1 part by weight of pyrogenic silica (Cab-O-siH-lS-S having a particle size of 7-10 millimicrons and a surface area of 300350 sq. meters/gram and a bulk density of 2.3 lbs/cuft.) are blended in a PREMIER Dispersator fitted with a 1 inch Duplex Head. The mixing time is 15 minutes. The blended SiB carbon-silica mixture is added to a 75.1 parts by weight of a perchloric acid dihydrate (72% perchloric acid) in the same type of dispersator. Again the blending is continued for 15 minutes. A highly viscous gel is obtained which has a Specific Impulse above 239. After 3 months storage at room temperature the mixture is found to be virtually unchanged.

EXAMPLE 2 In another embodiment using the same equipment and blending time and techniques before, silicon boride (SiB based propellant is prepared by blending a previously blended mixture of 3.5 parts by weight of the above described finely divided carbon thickener, and 25.1 parts by weight of silicon boride with 71.4 parts by weight HIRFNA (nitric acid as defined above). Again a viscous gel is obtained. The propellant has a Specific Impulse of 246 after blending. These properties are retained even after 3 months storage at room temperature.

EXAMPLE 3 In still another embodiment of this invention a propellant formulation is prepared having a boron carbidesilicon boride fuel. The preparation is as follows. Using the same equipment and techniques described earlier, a 12.5 parts by weight portion of boron carbide, 12.5 parts by weight of silicon boride, 3.5 parts by weight of the previously described carbon black are blended together for 20 minutes. At the end of this time 71.5 parts by weight portion of HIRF NA oxidizer is added and the blending is continued for an additional 30 minutes. The viscous propellant formulation had an initial Specific Impulse of about 252 which remained unchanged after 6 months storage at room temperature.

EXAMPLE 4 A 24.8 parts by weight portion of calcium carbide 3.5 parts by weight of the afore-described fine particle size silica are blended for 30 minutes. After the blending is completed 71.7 parts by weight of N is added to the blend and the blending is resumed for an additional minutes. A gel-like propellant having a Specific Impulse substantially above average is produced.

EXAMPLE 5 A 19.3 parts by weight portion of Boron Carbide, 3.5 parts by weight of finely divided silica are blended for minutes. At the end of this time a 77.2 parts by weight portion of 98% hydrogen peroxide (H 0 is blended in for an additional 20 minutes. The resultant propellant is a thick gel having a Specific Impulse of 277. This impulse remains substantially unchanged even after 90 days storage.

EXAMPLES 6, 7 and 8 Comparable propellant compositions can be obtained by combining stoichiometric proportions of concentrated (98 parts by weight) H 0 with various other fuels. In each instance 3.5 parts by weight of finely divided carbon black is used as the thixotroping agents. Typical formulations include lithium boride H 0 carbon black, tungsten carbide H 0 carbon black, boron carbide H O carbon black among others.

EXAMPLE 9 Preparation of B C/HlRFNA/Carbon Gel Materials: Boron Carbide 1000 mesh Carbon (Shawenigan Black) Particle size in the submicron area HIRFNA Normal Composition:

72.0% HNO 26.5% N0 0.7% HF 0.8% H 0 Experimental: The following materials are weighed out in the following proportions:

75.6% HIRFNA 20.9% 13 C 3.5% Carbon The HIRFNA mixture is then added to the mixing container, followed by the previously blended mixture of Boron Carbide and Carbon. The mixing is carried out by a Premier Dispersator fitted with a 1 inch Duplex Head. Mixing time varies from 3 minutes to /2 hour for batch sizes ranging from grams to 20 lbs. Transformer setting for the Dispersator is at 120. A gelled dispersion is obtained which has a Specific Impulse above 255. The mixture was tested and found to be stable after more than 6 months at room temperature.

EXAMPLE 10 Preparation of B C/N O /CAB-O-SIL GEL Materials:

Boron Carbide 1000 mesh Nitrogen tetroxide (N 0 Cab-O-Sil-(Pyrogenic colloidal silica). Particle size 0.007 to 0.010 microns Experimental:

The following materials are weighed out in the following proportions:

1.5% Cab-O-Sil Then all the propellant ingredients and mixing container are cooled down to 0C. Then l l O is added to the chilled container for mixing, followed by the previously prepared mixture of 8 C and Cab-O-Sil. The mixing is carried out by a Premier Dispersator fitted with a 1 inch Duplex Head. Mixing time for a 100 gm to 2 lb. batch is 3 minutes with the transformer setting on the Dispersator at 120. The mixing container is closed to the atmosphere during mixing and kept at 0C. during the entire mixing process. The resultant thixotropic gel has a Specific Impulse above 255 and is stable for more than 6 months.

EXAMPLE 1 1 Preparation of B C/HClO .2H O/CAB-O-SIL GEL Materials:

Boron Carbide. 1000 mesh Perchloric Acid Dihydrate (HClO .2H O) Cab-O-Sil-(Pyrogenic colloidal silica). Particle size 0.007 to 0.010 microns Experimental:

The following materials are weighed out in the following proportions:

79.6% HClO .2H O

3.5% Cab-O-Sil Then HCO .2H O is added to a previously prepared glass or polyethylene mixing container, followed by the previously weighed out and mixed B,,C and Cab-O-Sil. The mixing is carried out by a Premier Dispersator fitted with a 1 inch Duplex Head. Mixing time for a 100 gram to 2 lb. batch is 3 minutes with the transformer setting on the dispersator at 120. The resultant thixotropic gel has a Specific lmpulse above 240 and was found to be stable after more than 6 months.

The above 8 C based propellant formulation is especially advantageous as a propellant for torpedos and small submarines. For example, the Isp is in the order of 240 seconds, the lspd about 440 seconds and the Te about 3400K. In addition the major combustion products (H80 HCl and H are non-toxic substances. Additional advantages of this propellant formulation, particularly where use in submarines are contemplated, are the water solubility of the major combustion gases, low shock sensitivity and wakeless exhaust. Comparable advantages are obtained in the above formulation when stoichiometric quantities AlB and SiB fuels are substituted for the B C fuel.

As indicated by the previously disclosed illustrative embodiments, numerous modifications and variations can be made in the invention without departing from the inventive concept. Thus the metes and bounds of this invention can best be determined by an examination of the claims which follow.

We claim:

1. Novel thixotropic, monopropellant compositions comprising a mixture of a fuel selected from the group consisting of inorganic carbides, inorganic borides and inorganic boride-carbide mixtures, a liquid oxidizer selected from the group consisting of nitric acid, nitric acid enriched with N0 nitric acid enriched with N0 and HF, nitrogen tetroxide, hydrogen peroxide, and perchloric acid dihydrate and thixotroping agent selected from the group consisting of carbon, silica, clay, and mixtures thereof.

2. The thixotropic monopropellant compositions of claim 1 wherein the components are present in about the following proportions:

15-40 parts by weight of fuel 60-95 parts by weight of liquid oxidizer up to 10 parts by weight of thixotroping agents.

3. The thixotropic monopropellant compositions of claim 2 wherein up to 6 parts by weight or propellant adjuvants are present.

4. The thixotropic monopropellant compositions of claim 2 wherein the fuel is an inorganic carbide.

5. The thixotropic monopropellant compositions of claim 2 wherein the fuel is an inorganic boride.

6. The thixotropic monopropellant compositions of claim 2 wherein the fuel is an inorganic boride-carbide mixture.

7. A thixotropic monopropellant composition comprising a mixture of from about -40 parts by weight of a non-metallic boride, from about 60-95 parts by weight of a liquid oxidizer selected from the group consisting of nitric acid, nitric acid enriched with N0 nitric acid enriched with N0 and HF N 0 and concentrated H 0 and up to about l0 parts by weight of a thixotroping agent selected from the group consisting of carbon, silica, clay and mixtures thereof.

8. The thixotropic monopropellant composition of claim 7 wherein the non-metallic boride fuel is silicon boride.

9. The thixotropic monopropellant composition of claim 7 wherein the non-metallic boride fuel is zirconium boride.

10. A thixotropic monopropellant composition comprising from about 15-40 parts by weight of metallic boride fuel, from about 60-95 parts by weight of liquid oxidizer selected from group consisting of nitric acid, nitric acid enriched with N0 nitric acid enriched with N0 and HF, HC10,, N 0 and H 0 CIO F, N F C(NO L and O N.O.CH .CH .O.NO and up to about 10 parts by weight of a thixotroping agent selected from the group consisting of carbon, silica, clay, and mixtures thereof.

11. A thixotropic monopropellant composition comprising 15-40 parts by weight of aluminum boride (AlB fuel, from about 60-95 parts by weight of nitric acid enriched with N0 and up to about 10 parts by weight of a thixotroping agent selected from the group consisting of carbon, silica, clay, and mixtures thereof.

12. A thixotropic monopropellant composition comprising 15-40 parts by weight of beryllium boride fuel, from about 60-95 parts by weight of nitric acid enriched with N0 and up to about 10 parts by weight of a thixotroping agent selected from the group consisting of carbon, silica, clay, and mixtures thereof.

13. A thixotropic monopropellant composition comprising 15-40 parts by weight of calcium boride fuel, from about 60-95 parts by weight of N 0 oxidizer and up to about l0 parts by weight of a thixotroping agent selected from the group consisting of carbon, silica, clay, and mixtures thereof.

14. A thixotropic monopropellant composition comprising a mixture of from about 15-40 parts by weight of a non-metallic carbide fuel, from about 60-95 parts by weight of a liquid oxidizer selected from the group consisting of nitric acid enriched with N0 N 0,, and H 0 and up to about 10 parts by weight of a thixotroping agent selected from the group consisting of carbon, silica, clay, and mixtures thereof.

15. The thixotropic monopropellant composition of claim 14 wherein the non-metallic carbide fuel is boron carbide.

16. The thixotropic monopropellant composition of claim 14 wherein the non-metallic carbide fuel is silicon carbide.

17. The thixotropic monopropellant composition of claim 14 wherein the non-metallic carbide fuel is zirconium carbide.

18. The thixotropic monopropellant composition of claim 14 wherein the non-metallic carbide fuel is a mixture of boron carbide and silicon carbide.

19. A thixotropic monopropellant composition comprising a mixture of from about 15-40 parts by weight of metallic carbide fuel, from about 60-95 parts by weight of liquid oxidizer selected from the group consisting of N 0 and concentrated H 0 and up to about 10 parts by weight of a thixotropic agent selected from the group consisting of carbon. silica, clay, and mixtures thereof.

20. The thixotropic monopropellant composition of claim 19 wherein the metallic carbide fuel is aluminum carbide.

21. The thixotropic monopropellant composition of claim 19 wherein the metallic carbide fuel is beryllium carbide.

22. The thixotropic monopropellant composition of claim 19 wherein the metallic carbide fuel is calcium carbide.

23. A method of developing thrust in a reaction mtor, having a combustion chamber and a discharge opening, comprising the steps of igniting in said combustion chamber, a heterogeneous propellant composition of from about l-40 parts by weight of a solid fuel selected from the group consisting of inorganic carbides, inorganic borides and inorganic boride-carbide mixtures, from about 60-95 parts. by weight of a liquid oxidizer selected from the group consisting of perchloric acid dihydrate, concentrated H 0 and N 0 and up to about parts by weight of optional propellant adjuvants and a thixotroping agent selected from the group consisting of carbon, silica, clay, and mixtures thereof; and venting the combustion gases derived therefrom through said discharge opening.

24. The method of claim 23 wherein the liquid oxidizer is H 0 and the solid fuel is boron carbide.

25. The method of claim 23 wherein the liquid oxidizer is perchloric acid dihydrate and the solid fuel is boron carbide.

26. The method of claim 23 wherein the solid fuel is silicon carbide and the liquid oxidizer is perchloric acid dihydrate.

27. The method of claim 23 wherein the solid fuel is silicon carbide and the liquid oxidizer is concentrated H00...

28. The method of claim 23 wherein the solid fuel is silicon boride and the liquid oxidizer is perchloric acid dihydrate.

29. The method of claim 23 wherein the solid fuel is silicon boride and the liquid oxidizer is concentrated H90 30. A method of developing thrust in an aquatic vessel having a reaction motor. combustion chamber and discharge opening, comprising the steps of igniting in said combustion chamber a heterogeneous propellant composition of from about 15-40 parts by weight of a solid fuel selected from the group consisting of inorganic carbides, inorganic borides and inorganic carbide-boride mixtures, from about 60-95 parts by weight of a liquid oxidizerv selected from the group consisting of concentrated H 0 and perchloric acid dihydrate, and up to 10 parts by weight of optional propellant adjuvants and a thixotroping agent selected from the group consisting of carbon, silica, clay and mixtures thereof, and venting the combustion gases derived therefrom through said discharge opening.

31. The method of claim 30 wherein the liquid oxidizer is concentrated H 0 and the elemental solid fuel is boron carbide.

32. The method of claim 30 wherein the liquid oxidizer is concentrated H 0 and the elemental solid fuel is silicon carbide.

33. The method of claim 30 wherein the liquid oxidizer is concentrated H 0 and the elemental solid fuel is silicon boride.

34. The method of claim 30 wherein the liquid oxidizer is perchloric acid dihydrate and the elemental solid fuel is boron carbide.

35. The method of claim 30 wherein the liquid oxidizer is perchloric acid dihydrate and the elemental solid fuel is silicon carbide.

36. The method of claim 30 wherein the liquid oxidizer is perchloric acid dihydrate and the elemental solid fuel is silicon boride. 

1. NOVEL THIXOTROPIC, MONOPROPELLANT COMPOSITIONS COMPRISING A MIXTURE OF A FUEL SELECTED FROM THE GROUP CONSISTING OF INORGANIC CARBIDES, INORGANIC BORIDES AND INORGANIC BORIDECARBIDE MIXTURES, A LIQUID OXIDIZER SELECTED FROM THE GROUP CONSISTING OF NITRIC ACID, NITRIC ACID ENRICHED WITH NO2, NITRIC ACID ENRICHED WITH NO2 AND HF, NITROGEN TETROXIDE, HYDROGEN PEROXIDE, AND PERCHLORIC ACID DIHYDRATE AND THIXOTROPING AGENT SELECTED FROM THE GROUP CONSISTING OF CARBON, SILICA, CLAY, AND MIXTURES THEREOF.
 2. The thixotropic monopropellant compositions of claim 1 wherein the components are present in about the following proportions: 15-40 parts by weight of fuel 60-95 parts by weight of liquid oxidizer up to 10 parts by weight of thixotroping agents.
 3. The thixotropic monopropellant compositions of claim 2 wherein up to 6 parts by weight or propellant adjuvants are present.
 4. The thixotropic monopropellant compositions of claim 2 wherein the fuel is an inorganic carbide.
 5. The thixotropic monopropellant compositions of claim 2 wherein the fuel is an inorganic boride.
 6. The thixotropic monopropellant compositions of claim 2 wherein the fuel is an inorganic boride-carbide mixture.
 7. A thixotropic monopropellant composition comprising a mixture of from about 15-40 parts by weight of a non-metallic boride, from about 60-95 parts by weight of a liquid oxidizer selected from the group consisting of nitric acid, nitric acid enriched with NO2, nitric acid enriched with NO2 and HF N2O4, and concentrated H2O2, and up to about 10 parts by weight of a thixotroping agent selected from the group consisting of carbon, silica, clay and mixtures thereof.
 8. The thixotropic monopropellant composition of claim 7 wherein the non-metallic boride fuel is silicon boride.
 9. The thixotropic monopropellant composition of claim 7 wherein the non-metallic boride fuel is zirconium boride.
 10. A thixotropic monopropellant composition comprising from about 15-40 parts by weight of metallic boride fuel, from about 60-95 parts by weight of liquid oxidizer selected from group consisting of nitric acid, nitric acid enriched with NO2, nitric acid enriched with NO2 and HF, HC104, N2O4, and H2O2, ClO3F, N2F4, C(NO2)4 and O2N.O.CH2.CH2.O.NO2 and up to about 10 parts by weight of a thixotroping agent selected from the group consisting of carbon, silica, clay, and mixtures thereof.
 11. A thixotropic monopropellant composition comprising 15-40 parts by weight of aluminum boride (AlB12) fuel, from about 60-95 parts by weight of nitric acid enriched with NO2, and up to about 10 parts by weight of a thixotroping agent selected from the group consisting of carbon, silica, clay, and mixtures thereof.
 12. A thixotropic monopropellant composition comprising 15-40 parts by weight of beryllium boride fuel, from about 60-95 parts by weight of nitric acid enriched with NO2, and up to about 10 parts by weight of a thixotroping agent selected from the group consisting of carbon, silica, clay, and mixtures thereof.
 13. A thixotropic monopropellant composition comprising 15-40 parts by weight of calcium boride fuel, from about 60-95 parts by weight of N2O4 oxidizer and up to about 10 parts by weight of a thixotroping agent selected from the group consisting of carbon, silica, clay, and mixtures thereof.
 14. A thixotropic monopropellant composition comprising a mixture of from about 15-40 parts by weight of a non-metallic carbide fuel, from about 60-95 parts by weight of a liquid oxidizer selected from the group consisting of nitric acid enriched with NO2, N2O4, and H2O2, and up to about 10 parts by weight of a thixotroping agent selected from the group consisting of carbon, silica, clay, and mixtures thereof.
 15. The thixotropic monopropellant composition of claim 14 wherein the non-metallic carbide fuel is boron carbide.
 16. The thixotropic monopropellant composition of claim 14 wherein the non-metallic carbide fuel is silicon carbide.
 17. The thixotropic monopropellant composition of claim 14 wherein the non-metallic carbide fuel is zirconium carbide.
 18. The thixotropic monopropellant composition of claim 14 wherein the non-metallic carbide fuel is a mixture of boron carbide and silicon carbide.
 19. A thixotropic monopropellant composition comprising a mixture of from about 15-40 parts by weight of metallic carbide fuel, from about 60-95 parts by weight of liquid oxidizer selected from the group consisting of N2O4 and concentrated H2O2, and up to about 10 parts by weight of a thixotropic agent selected from the group consisting of carbon, silica, clay, and mixtures thereof.
 20. The thixotropic monopropellant composition of claim 19 wherein the metallic carbide fuel is aluminum carbide.
 21. The thixotropic monopropellant composition of claim 19 wherein the metallic carbide fuel is beryllium carbide.
 22. The thixotropic monopropellant composition of claim 19 wherein the metallic carbide fuel is calcium carbide.
 23. A METHOD OF DEVELOPING THRUST IN A REACTION MOTOR, HAVING A COMBUSTION CHAMBER AND A DISCHARGE OPENING, COMPRISING THE STEPS OF IGNITING IN SAID COMBUSTION CHAMBER, A HETEROGENEOUS PROPELLANT COMPOSITION OF FROM ABOUT 15-40 PARTS BY WEIGHT OF A SOLID FUEL SELECTED FROM THE GROUP CONSISTING OF INORGANIC CARBIDES, INORGANIC BORIDES AND INORGANIC BORIDE-CARBIDE MIXTURES, FROM ABOUT 60-95 PARTS BY WEIGHT OF A LIQUID OXIDIZER SELECTED FROM THE GROUP CONSISTING OF PERCHLORIC ACID DIHYDRATE, CONCENTRATED H2O2 AND N2O4, AND UP TO ABOUT 10 PARTS BY WEIGHT OF OPTIONAL PROPELLANT ADJUVANTS AND A THIXOTROPING AGENT SELECTED FROM THE GROUP CONSISTING OF CARBON, SILICA, CLAY, AND MIXTURES THEREOF; AND VENTING THE COMBUSTION GASES DERIVED THEREFROM THROUGH SAID DISCHARGE OPENING.
 24. The method of claim 23 wherein the liquid oxidizer is H2O2 and the solid fuel is boron carbide.
 25. The method of claim 23 wherein the liquid oxidizer is perchloric acid dihydrate and the solid fuel is boron carbide.
 26. The method of claim 23 wherein the solid fuel is silicon carbide and the liquid oxidizer is perchloric acid dihydrate.
 27. The method of claim 23 wherein the solid fuel is silicon carbide and the liquid oxidizer is concentrated H2O2.
 28. The method of claim 23 wherein the solid fuel is silicon boride and the liquid oxidizer is perchloric acid dihydrate.
 29. The method of claim 23 wherein the solid fuel is silicon boride and the liquid oxidizer is concentrated H2O2.
 30. A method of developing thrust in an aquatic vessel having a reaction motor, combustion chamber and discharge opening, comprising the steps of igniting in said combustion chamber a heterogeneous propellant composition of from about 15-40 parts by weight of a solid fuel selected from the group consisting of inorganic carbides, inorganic borides and inorganic carbide-boride mixtures, from about 60-95 parts by weight of a liquid oxidizer selected from the group consisting of concentrated H2O2 and perchloric acid dihydrate, and up to 10 parts by weight of optional propellant adjuvants and a thixotroping agent selected from the group consisting of carbon, silica, clay and mixtures thereof, and venting the combustion gases derived therefrom through said discharge opening.
 31. The method of claim 30 wherein the liquid oxidizer is concentrated H2O2 and the elemental solid fuel is boron carbide.
 32. The method of claim 30 wherein the liquid oxidizer is concentrated H2O2 and the elemental solid fuel is silicon carbide.
 33. The method of claim 30 wherein the liquid oxidizer is concentrated H2O2 and the elemental solid fuel is silicon boride.
 34. The method of claim 30 wherein the liquid oxidizer is perchloric acid dihydrate and the elemental solid fuel is boron carbide.
 35. The method of claim 30 wherein the liquid oxidizer is perchloric acid dihydrate and the elemental solid fuel is silicon carbide.
 36. The method of claim 30 wherein the liquid oxidizer is perchloric acid dihydrate and the elemental solid fuel is silicon boride. 